Rep Power: 146

So I got another 2005 Civic (Reverb) to replace the one some thieves pulled apart. Ugh, should have just gotten my old car back from the insurance and fixed it.... Anyway, moving on...

So got this Civic with 220k Km on it. It had some minor mechanical issues but I've got it all running and it's on the road now. It is probably important to note that some previous owner put a Magnaflow exhaust on it. I'm not really happy with it since it's freaking loud and I sound like a friggin racer but I guess the stainless tip looks pretty nice.

Anyway, as I am driving at highway speed (110km/h - 130 km/h) I hear this periodic (period of about 0.5, as in about two times per second) resonance coming from the engine. It sounds like:

mmmmmMMMMMMmmmmmmmMMMMMMMmmmmmmMMMMMMmmmmmMMMMMMmm mmmm

|--------------1 second----------------|

It is NOT the tires as I can hear the tires separately and as soon as I let my foot of the accelerator it stops as well. I know what the tires sound like and I know what the engine sounds like... it is definitely engine noise.

There are no engine codes and I just replaced the engine air filer and plugs (Honda filter and the proper NGK iridium plugs) and the noise was there exactly the same before and after. It isn't necessarily causing any problems with the car but since I commute 1 hour to work it is annoying as hell.

Any leads to start with? Could it be the fact that I have this Magnaflow exhaust and not a standard exhaust?

Thanks.

 
Rep Power: 211

HmmmMMMmmmMMM? Could be a number of things and may be hard to reproduce if it's intermittent. Post a video of the noise if you can capture it.

 
Rep Power: 519

This may sound 'out there' but it's possible it may just be fuel control.

There are times and engines...sometimes I notice, I can hear the differences in steady speed running as the O2 sensor cycles and fuel control goes rich and lean accordingly. That cycling can be in the quarter to half second rate.

Not saying that's what you hear, but it popped into my head so I wrote it down.

 
Rep Power: 146

I'll try and get one. Problem is, is that it's not particularly loud and may blend into the background with an iPhone microphone, but I'll try...

I wonder if I could see this with DashCommand while driving? I haven't had too much experience with it but it's worth looking into. I think there is a section where it shows you what the A/F sensor is sending in terms of lean/rich.

 
Rep Power: 519

How quick is the update or refresh rate?


Put a quiet muffler on it, and have the exhaust shop stick a chrome tip on it.
Problem solved!

 
Rep Power: 150

If you can hear anything above the exhaust, it's probably getting ready to blow up. Least what I hope when I get beside or behind a car with one of those stove pipes.

 
Rep Power: 519

^I like my cars quiet but I like my bike LOUD.

 
Rep Power: 257

yeah the MMMhhhhMMhhhh sound definitely means your car is going to explode in the near future. i suggests you put sticky tape over any check engine lights that should give you some time.

 
Rep Power: 211